JP5261626B2 - Polarizer with polyvinyl alcohol resin layer - Google Patents

Description

  The present invention relates to a polarizer including a polyvinyl alcohol-based resin layer on which iodine is adsorbed.

  A manufacturing method is known in which a polyvinyl alcohol film is dyed with a dye-containing dye solution and then stretched to obtain a polarizer (for example, Patent Document 1). In the above production method, the dyed and stretched film is immersed in an aqueous potassium iodide solution to perform iodine ion impregnation treatment, and further immersed in an alcohol solution to perform an alcohol solution immersion treatment.

  The polarizer obtained by this production method has a small yellowishness and little hue change even in a heating environment. The reason for the small yellowness is that the absorbance is almost constant in the entire wavelength region of visible light.

  However, the above polarizer has a problem that the degree of polarization is low.

JP 2003-270440 A

  As a method for obtaining a polarizer, a polyvinyl alcohol film is dyed with a dyeing solution containing iodine, then stretched, immersed in an aqueous potassium iodide solution to be impregnated with iodine ions, and further immersed in an alcoholic solution to obtain an alcoholic solution. A method for performing an immersion treatment is known. However, the polarizer obtained by this manufacturing method has a problem that the degree of polarization is low.

  The present invention provides a polarizer having a high degree of polarization comprising a polyvinyl alcohol-based resin layer on which iodine is adsorbed.

In the first aspect, the gist of the present invention is as follows.
A polarizer comprising a polyvinyl alcohol-based resin layer iodine is adsorbed, the polyvinyl alcohol-based resin layer is a thickness of 0.4~7μm by being stretched, oriented in a certain direction The polymer chain includes a highly oriented crystallization part, and the iodine adsorbed on the polyvinyl alcohol resin layer is a polyiodide adsorbed on the crystallization part of the polyvinyl alcohol resin layer. present in the form of iodine ion complex in the polyvinyl alcohol resin layer, giving absorption dichroism in the polarizer, the polarizer is a absorbance from 0.359 to 0.380, polarization degree 99.9% A polarizer having the above optical characteristics.
The polarizer or is in the absorbance of the optical properties 0.362 to 0.377, polarization degree can be made showing the optical characteristics of the above 99.9%.
In the second aspect, the gist of the present invention is as follows.
A polarizer comprising a polyvinyl alcohol-based resin layer on which iodine is adsorbed, wherein the polyvinyl alcohol-based resin layer has a thickness of 0.4 to 7 μm by being stretched, and is a polymer oriented in a certain direction The polymer chain includes a highly oriented crystallization part, and the iodine adsorbed on the polyvinyl alcohol resin layer is a polyiodine ion adsorbed on the crystallization part of the polyvinyl alcohol resin layer. It exists in the polyvinyl alcohol resin layer in the form of a complex to give the polarizer absorptive dichroism, and the polarizer has an optical characteristic with an absorbance of 0.377 or less and a polarization degree of 99.95% or more. A polarizer characterized by what is shown.
In addition, the polarizer may exhibit an optical characteristic in which the absorbance of the optical characteristic is 0.362 to 0.377 and the polarization degree is 99.95% or more.
In the first and second aspects, the polarizer, the polyiodine ion complex, I ₃ ^- and I ₅ ^- in the form of, be assumed to be adsorbed to the crystallization of the polymer chains it can.

  As a result of intensive studies to solve the above-described problems, the present inventors have found that a polarizer having a high degree of polarization can be obtained by sequentially performing the following three steps A to C. Each process is demonstrated with reference to FIGS. 1 and 2 show a case where a polyvinyl alcohol-based resin layer is formed on a support and the polyvinyl alcohol-based resin layer is stretched together with the support.

  FIG. 1A is a schematic cross-sectional view of the polyvinyl alcohol-based resin layer 10 before stretching, formed on the support 30. The polyvinyl alcohol-based resin layer 10 includes an amorphous part 11 and a crystallized part 12. The crystallized portion 12 is randomly present in the amorphous portion 11. An arrow 13 indicates the extending direction of the next step.

[Step A] Stretching before dyeing First, the polyvinyl alcohol-based resin layer 10 is stretched together with the support 30. The polyvinyl alcohol-based resin layer 10 is called a stretched layer 14 after stretching. FIG. 1B is a schematic cross-sectional view of the stretched layer 14. The first point in the method for producing the polarizer of the present invention is to stretch the polyvinyl alcohol resin layer 10 before dyeing. Arrow 15 indicates the stretching direction. By stretching, a polymer chain (not shown) in the stretched layer 14 is crystallized, and a crystallized portion 17 with higher orientation is generated in the amorphous portion 16.

[Step B] Excessive dyeing Next, the stretched layer 14 is dyed. Staining is an iodine adsorption process. The stretched layer 14 is called a dyed layer 18 after dyeing. FIG. 2C is a schematic cross-sectional view of the dyed layer 18. The second point in the method for producing the polarizer of the present invention is to immerse the stretched layer 14 in a dyeing solution containing iodine to over-dye. The excess stain, absorbance A _B determined from the tristimulus values Y, means that stained as 0.4 or more. The subscript _B of the absorbance A _B represents the process B.

The absorbance A obtained from the tristimulus value Y of a general polarizer is about 0.37. For example, the absorbance A of a polarizer having a transmittance T = 43% is A = 0.367. Therefore, staining, such as a method for producing the polarizer of the present invention, the absorbance A _B becomes 0.4 or more is considered excessive staining.

The polymer chain crystallization part 17 is less dyed than the amorphous part 16. However, iodine can be sufficiently adsorbed also to the crystallization part 17 by dyeing the stretched layer 14 excessively. The adsorbed iodine forms a polyiodine ion complex 19 such as I ₃ ⁻ or I ₅ ⁻ in the dyed layer 18. The polyiodine ion complex 19 exhibits absorption dichroism in the visible light region (wavelength 380 nm to 780 nm).

[Step C] Decolorization (removal of part of iodine)
Next, a part of the iodine adsorbed on the dyed layer 18 is removed. This is called decolorization. After decolorization, the dyed layer 18 is called a polarizer 20. Iodine is adsorbed on the dyed layer 18 in the form of a polyiodine ion complex 19. FIG. 2D is a schematic cross-sectional view of the polarizer 20. The third point in the method for producing the polarizer of the present invention is to remove part of the polyiodine ion complex 19 from the overstained dyed layer 18. In order to remove the polyiodine ion complex 19 from the dyed layer 18, for example, the dyed layer 18 is immersed in an aqueous solution of potassium iodide (decolorizing solution). At this time, the absorbance _{A C} is to decrease 0.03 to 0.7, to remove polyiodine ion complex 19. However, the absorbance of the dyed layer should not be less than 0.3. The suffix _C of absorbance A _C represents step C.

  When the polyiodine ion complex 19 is removed, the polyiodine ion complex 19 adsorbed on the amorphous part 16 is preferentially removed. As a result, a relatively large amount of the polyiodine ion complex 19 adsorbed on the crystallization part 17 remains.

  The polyiodine ion complex 19 adsorbed on the amorphous part 16 has a small contribution to the absorption dichroism. On the other hand, the polyiodine ion complex 19 adsorbed on the crystallization part 17 greatly contributes to absorption dichroism. However, the polyiodine ion complex 19 adsorbed on the amorphous part 16 and the polyiodine ion complex 19 adsorbed on the crystallization part 17 increase the absorbance in the same manner. According to the method for producing a polarizer of the present invention, it is possible to preferentially remove the polyiodine ion complex 19 adsorbed on the amorphous part 16, which increases the absorbance even though the contribution to the absorption dichroism is small. . Therefore, the polyiodine ion complex 19 adsorbed on the crystallization part 17 having a large contribution to the absorption dichroism is relatively increased. A large contribution to absorption dichroism is a high degree of polarization. Therefore, by the method for producing a polarizer of the present invention, a polarizer 20 having a high degree of polarization can be obtained for a low absorbance.

  According to the method for producing a polarizer of the present invention, since the polyiodine ion complex 19 adsorbed on the crystallization part 17 greatly contributes to the absorption dichroism, the degree of polarization is high while the absorbance is low. A polarizer 20 is obtained.

(A) Schematic diagram showing the pre-stage of the manufacturing process of the polarizer of the present invention, (b) Schematic diagram showing manufacturing process A of the polarizer of the present invention (C) Schematic diagram showing manufacturing process B of the polarizer of the present invention, (d) Schematic diagram showing manufacturing process C of the polarizer of the present invention. The schematic diagram which shows the manufacturing process of the polarizer of this invention. Polarizer absorbance vs. degree of polarization graph Absorbance vs. degree of polarization of stained layer

[Method for Producing the Polarizer of the Present Invention]
FIG. 3 is a schematic view showing a production process of the polarizer of the present invention. The method for producing the polarizer of the present invention is a method for producing the polarizer 20 comprising a polyvinyl alcohol-based resin layer containing iodine.

  The unprocessed polyvinyl alcohol-based resin layer 10 in the form of a film formed on the support 30 is sequentially pulled out from the feeding portion 21 together with the support 30 for processing.

  In Step A, the polyvinyl alcohol-based resin layer 10 is stretched while passing between the stretching rolls 22 together with the support 30 to become the stretched layer 14.

In step B, the stretched layer 14 is immersed in the dyeing solution 23 containing iodine to become the dyed layer 18. Of the dyed layer 18, the absorbance _{A B} determined from the tristimulus value Y is 0.4~1.0 (T = 40% ~10% ).

In step C, the dyed layer 18 is immersed in the decolorizing solution 24 (potassium iodide aqueous solution), and a part of iodine is removed to form the polarizer 20. At this time, the absorbance _{A C} of the polarizer 20, as compared to the absorbance _{A B} Step C immediately before the dyed layer 18, decreases from 0.03 to 0.7. However, the absorbance of the dyed layer should not be less than 0.3.

  The completed polarizer 20 is taken up by the take-up unit 25.

  The method for producing the polarizer of the present invention may include other steps as long as the steps A, B, and C are included in this order. As another process, for example, the dyed layer 18 is immersed in a crosslinking liquid (an aqueous solution containing boric acid and, if necessary, potassium iodide) between the process B and the process C, and a polyvinyl alcohol-based resin layer There is a step of crosslinking. Moreover, there is a step of drying the polarizer 20 obtained in the step C.

[Step A]
Step A used in the method for producing a polarizer of the present invention is a step of obtaining a stretched layer 14 by stretching the polyvinyl alcohol-based resin layer 10.

  The polyvinyl alcohol-based resin layer 10 used in the method for producing a polarizer of the present invention is obtained by forming a polyvinyl alcohol-based resin into a layer shape. The polyvinyl alcohol resin layer 10 is preferably formed on the support 30.

  The polyvinyl alcohol resin is typically obtained by saponifying a polyvinyl acetate resin. The polyvinyl alcohol resin used in the method for producing the polarizer of the present invention is, for example, polyvinyl alcohol or an ethylene-vinyl alcohol copolymer. The saponification degree of the polyvinyl alcohol-based resin used in the method for producing the polarizer of the present invention is preferably 85 mol% to 100 mol% because water resistance becomes high and stretching at a high magnification becomes possible. 95 mol% to 100 mol% is more preferable, and 98 mol% to 100 mol% is more preferable. The degree of polymerization of the polyvinyl alcohol-based resin used in the method for producing the polarizer of the present invention can increase the degree of polarization by increasing the polyiodine ion complex adsorbed on the crystallization part 17, and therefore, 1,000 to 10,000. Is preferred.

  As a method of stretching the polyvinyl alcohol-based resin layer 10, any known stretching method such as roll stretching or tenter stretching is used. The draw ratio of the polyvinyl alcohol-based resin layer 10 is usually 3 to 7 times the original length.

  The stretching of the polyvinyl alcohol-based resin layer 10 is preferably dry stretching. Dry stretching is stretching in the air. The dry stretching is preferable because the crystallinity can be higher than the wet stretching. In this case, the stretching temperature is preferably 80 ° C to 170 ° C, and more preferably 130 ° C to 170 ° C. By setting the stretching temperature to 130 ° C. or higher, crystallization of the polymer chain in the polyvinyl alcohol-based resin layer 10 can be promoted. As a result, the polyiodine ion complex 19 adsorbed on the crystallization part 17 can be increased, and the degree of polarization can be increased. Further, by setting the stretching temperature to 170 ° C. or less, it is possible to prevent the crystallization of the polymer chain from proceeding excessively and to shorten the dyeing time in the process B. The polyvinyl alcohol-based resin layer 10 is preferably stretched so that the degree of crystallinity after stretching is 20% to 50%, more preferably 32% to 50%. If the degree of crystallization after stretching is 20% to 50%, the polyiodine ion complex 19 adsorbed on the crystallization part 17 increases, and the degree of polarization can be increased.

  The polyvinyl alcohol-based resin layer 10 may contain other additives other than iodine. Examples of other additives include surfactants, antioxidants, and crosslinking agents.

The film thickness t ₀ of the polyvinyl alcohol-based resin layer 10 before stretching is usually 2 μm to 30 μm, preferably 3 μm to 15 μm. Since the polyvinyl alcohol resin layer 10 before stretching is thin, when it is difficult to stretch alone, the polyvinyl alcohol resin layer 10 is formed on the support 30 and the polyvinyl alcohol resin layer together with the support 30. 10 is stretched.

The film thickness t ₁ of the stretched layer 14 is usually 0.4 μm to 7 μm, and preferably 0.6 μm to 5 μm. If the film thickness t ₁ of the stretched layer 14 is 5 μm or less, the target absorbance can be dyed in a short time.

[Step B]
In Step B used in the method for producing a polarizer of the present invention, the stretched layer 14 obtained in Step A is immersed in a dyeing solution 23 containing iodine to obtain a dyed layer 18. Absorbance _{A B} of the dyed layer 18 is preferably, 0.4~1.0 (T = 40% ~10 %). Absorbance _{A B} of the dyed layer 18, more preferably 0.5~1.0 (T = 31.6% ~10% ). Absorbance A _B of the dyed layer 18, (if T is greater than 40%) of less than 0.4, the crystallization portion 17 of the polymer chains, may not be adsorbed enough polyiodine ion complex 19.

In the method for producing the polarizer of the present invention, the absorbance A is calculated by the formula (1).
A = log ₁₀ (1 / T) (1)
Here, the transmittance T is the value of the tristimulus value Y in the XYZ color system based on the 2-degree visual field of JIS Z 8701 (1995). In this specification, the value of transmittance T is expressed as a percentage, where T = 1 is 100%.

Of the dyed layer 18, the tristimulus values absorbance _{A B} obtained from Y may be placed in the prescribed range immediately after the step B (0.4 to 1.0), or may be subsequently changed.

  The staining solution 23 used in the method for producing a polarizer of the present invention is usually an aqueous solution containing iodine and an alkali iodide or ammonium iodide. In the staining solution 23, alkali iodide or ammonium iodide is used to increase the solubility of iodine in water. The iodine content of the dyeing liquid 23 is preferably 1.1 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. When potassium iodide is used as the alkali iodide, the potassium iodide content of the dyeing solution 23 is preferably 3 to 30 parts by weight with respect to 100 parts by weight of water.

  The temperature and immersion time of the staining solution 23 are appropriately set so as to satisfy the characteristics specified in the method for producing the polarizer of the present invention, depending on the concentration of the staining solution 23 and the thickness of the stretched layer 14. The temperature of the staining liquid 23 is preferably 20 ° C to 40 ° C. The immersion time in the staining solution 23 is preferably 60 seconds to 1200 seconds.

[Step C]
In Step C used in the method for producing a polarizer of the present invention, a part of the polyiodine ion complex 19 is removed from the dyed layer 18 obtained in Step B to obtain the polarizer 20. Removal of polyiodine ion complex 19, the absorbance _{A C} of the polarizer 20 is, than the absorbance _{A B} of the dyed layer 18, to be lower 0.03 to 0.7. However, the absorbance A _B of the dyed layer is to not less than 0.3.

Polarizer 20, the absorbance _{A C} obtained from the tristimulus value Y is preferably, 0.3~0.4 (T = 50% ~40 %). To obtain the absorbance _{A C} of the above range, the decline ΔA in absorbance at Step _{C (=} A B -A C) is preferably a 0.03 to 0.7. The absorbance decrease width ΔA in step C is more preferably 0.05 to 0.65. When the absorbance decrease width ΔA is less than 0.03, the polarizer 20 having a high degree of polarization may not be obtained.

  When a part of the polyiodine ion complex 19 is removed from the dyed layer 18, for example, an aqueous solution of alkali iodide or ammonium iodide is used. An aqueous solution of alkali iodide or ammonium iodide used for this purpose is referred to as decolorizing solution 24. The process of removing part of the polyiodine ion complex 19 from the dyed layer 18 is called decolorization. For decolorization, the dyeing layer 18 may be immersed in the decoloring solution 24, or the decoloring solution may be applied to or sprayed on the surface of the dyeing layer 18.

  In the decolorizing liquid 24, the polyiodine ion complex 19 is easily eluted from the dyed layer 18 by the action of iodine ions. Iodine ions are obtained from alkali iodides such as potassium iodide, sodium iodide, lithium iodide, magnesium iodide, and calcium iodide. Alternatively, iodine ions are obtained from ammonium iodide. The iodine ion concentration of the decolorizing solution 24 is preferably sufficiently lower than the iodine ion concentration of the staining solution 23. When potassium iodide is used, the potassium iodide content of the decolorizing solution 24 is preferably 1 to 20 parts by weight with respect to 100 parts by weight of water.

  The temperature and immersion time of the decolorizing liquid 24 are appropriately set according to the film thickness of the dyed layer 18. The temperature of the decolorizing liquid 24 is preferably 45 ° C to 75 ° C. The immersion time in the decolorizing liquid 24 is preferably 20 seconds to 600 seconds.

[Polarizer of the present invention]
The polarizer 20 of the present invention comprises a polyvinyl alcohol resin layer containing iodine. The polyvinyl alcohol-based resin layer is stretched and dyed and has polymer chains oriented in a certain direction. Iodine forms a polyiodine ion complex 19 such as I ₃ ⁻ or I ₅ ⁻ in the polyvinyl alcohol-based resin layer, and exhibits absorption dichroism in the visible light region (wavelength 380 nm to 780 nm).

The film thickness t ₃ of the polarizer 20 is usually the same as the film thickness t ₁ of the stretched layer 14, and is usually 0.4 μm to 7 μm, preferably 0.6 μm to 5 μm.

According to the method for producing the polarizer of the present invention, absorbance _{A C} is 0.37 (T = 43%) extent, the degree of polarization of the polarizer 20 thickness _{t 3} is 5μm or less, 99.9% This can be done.

[Example 1]
(1) A 7% by weight aqueous solution of polyvinyl alcohol was applied to the surface of a support made of a norbornene-based resin film having a film thickness of 150 μm (ARTON manufactured by JSR) to form a polyvinyl alcohol film. The degree of polymerization of polyvinyl alcohol was 4,200, and the degree of saponification was 99% or more.
(2) The polyvinyl alcohol film and the support were dried at 80 ° C. for 8 minutes, and a polyvinyl alcohol layer having a thickness of 7 μm was formed on the support to obtain a laminate of the polyvinyl alcohol layer and the support.
(3) The laminate of the polyvinyl alcohol layer and the support was dry uniaxially stretched using a biaxial stretching machine (manufactured by Iwamoto Seisakusho). The stretching temperature was 150 ° C. The draw ratio was 4.8 times the original length. As a result of stretching, a laminate of a stretched layer and a support was obtained. The support is also stretched at the same magnification as the stretch layer.
(4) A laminate of the dyed layer and the support is immersed in a dyeing solution comprising an aqueous solution containing iodine and potassium iodide, and a polyiodide ion complex is adsorbed and oriented in the drawn layer. Got. The immersion time in the staining solution was 600 seconds. The liquid temperature of the staining liquid was 25 ° C. The composition of the staining solution was iodine: potassium iodide: water = 1.1: 7.8: 100 by weight ratio. The absorbance immediately after staining was 0.602.
(5) The laminate of the dyed layer and the support was immersed in a decolorizing solution containing potassium iodide, and a part of the polyiodine ion complex in the dyed layer was removed. The composition of the decolorizing solution was water: potassium iodide = 100: 5.3 by weight ratio. The liquid temperature of the decolorizing liquid was 60 ° C. By adjusting the immersion time in the decoloring solution, five types of samples were produced in which the absorbance of the completed polarizer was 0.357 to 0.377.
(6) The partially decolored dyed layer / support laminate was immersed in a crosslinking solution containing boric acid and potassium iodide. The composition of the crosslinking liquid was, by weight, water: boric acid: potassium iodide = 100: 11.8: 5.9. The immersion time in the crosslinking solution was 60 seconds. The liquid temperature of the crosslinking liquid was 60 ° C.
(7) The laminate of the dyed layer and the support subjected to the crosslinking treatment was dried at 60 ° C. for 120 seconds.
As described above, a laminate of a polarizer (film thickness 2.9 μm) and a support was formed. A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG. FIG. 5 shows a graph of absorbance (A _B ) versus polarization degree of the dyed layer.

[Example 2]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 2.9 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) The time immediately after dyeing was adjusted to 0.921 by adjusting the immersion time in the staining solution.
(2) By adjusting the immersion time in the decolorizing solution, five types of samples in which the absorbance of the completed polarizer was 0.359 to 0.377 were prepared.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG. FIG. 5 shows a graph of absorbance (A _B ) versus polarization degree of the dyed layer.

[Example 3]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 2.9 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) The immersion time in the staining solution was adjusted so that the absorbance immediately after staining was 0.420.
(2) Adjusting the immersion time in the decolorizing solution, four types of samples were produced in which the absorbance of the finished polarizer was 0.362 to 0.377.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG. FIG. 5 shows a graph of absorbance (A _B ) versus polarization degree of the dyed layer.

[Example 4]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 2.9 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) The time immediately after dyeing was adjusted to 0.959 by adjusting the immersion time in the staining solution.
(2) Adjusting the immersion time in the decolorizing solution, four types of samples were produced in which the absorbance of the finished polarizer was 0.357 to 0.376.
(3) The stretching temperature was 100 ° C., and the stretching ratio was 4.5 times the original length.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Example 5]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 3.5 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) A 5% by weight aqueous solution of polyvinyl alcohol was applied.
(2) The stretching temperature was 140 ° C., and the stretching ratio was 4.0 times the original length.
(3) The composition of the staining solution was, by weight, iodine: potassium iodide: water = 1: 7: 92, and the immersion time in the staining solution was 300 seconds.
(4) The absorbance immediately after staining was 0.613.
(5) The content of potassium iodide in the decolorizing solution was, by weight, water: potassium iodide = 95: 5. The immersion time in the decolorizing solution was 30 seconds, and the absorbance of the completed polarizer was 0.380.
(6) The composition of the crosslinking liquid was, by weight ratio, water: boric acid: potassium iodide = 85: 10: 5.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Example 6]
In the same manner as in Example 5, a laminate of a polarizer (film thickness: 3.5 μm) and a support was formed. However, it differs from Example 5 in the following points.
(1) The immersion time in the staining solution was 600 seconds. The absorbance immediately after staining was 0.417.
(2) The immersion time in the decolorizing solution was 2 seconds. The absorbance of the completed polarizer was 0.380.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Example 7]
In the same manner as in Example 5, a laminate of a polarizer (film thickness: 3.5 μm) and a support was formed. However, it differs from Example 5 in the following points.
(1) A 200 μm-thick amorphous polyethylene terephthalate film (Novaclear SG007 manufactured by Mitsubishi Plastics) was used as the support.
(2) The stretching temperature was 110 ° C.
(3) The composition of the staining solution was iodine: potassium iodide: water = 0.2: 1.4: 98.4 by weight.
(4) The immersion time in the dyeing solution was 600 seconds. The absorbance immediately after staining was 0.577.
(5) The immersion time in the decolorizing solution was 8 seconds, and the absorbance of the completed polarizer was 0.380.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Comparative Example 1]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 2.9 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) By adjusting the immersion time in the staining solution, four types of samples were produced in which the absorbance of the completed polarizer was 0.367 to 0.387.
(2) No decolorization step was performed.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG. FIG. 5 shows a graph of absorbance (A _B ) versus polarization degree of the dyed layer.

[Comparative Example 2]
In the same manner as in Example 1, a laminate of a polarizer (film thickness: 2.9 μm) and a support was formed. However, it differs from Example 1 in the following points.
(1) By adjusting the immersion time in the staining solution, four types of samples in which the absorbance of the completed polarizer was 0.367 to 0.384 were prepared.
(2) No decolorization step was performed.
(3) The stretching temperature was 100 ° C., and the stretching ratio was 4.5 times the original length.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Comparative Example 3]
In the same manner as in Example 5, a laminate of a polarizer (film thickness: 3.5 μm) and a support was formed. However, it differs from Example 5 in the following points.
(1) The composition of the staining solution was iodine: potassium iodide: water = 0.5: 3.5: 96.0 by weight.
(2) The immersion time in the staining solution was 25 seconds. The absorbance immediately after staining was 0.395.
(3) No decolorization step was performed.
A graph of the absorbance (A _C ) of the polarizer versus the degree of polarization is shown in FIG.

[Evaluation]
FIG. 4 illustrates a graph of absorbance (A _C ) versus polarization degree of a polarizer.
(1) When Examples 1-3 are compared, it becomes Example 2, Example 1, and Example 3 in order with a high polarization degree. This is the order of decreasing absorbance due to decolorization. The decrease in absorbance in Example 2 is 0.544 to 0.562, the decrease in absorbance in Example 1 is 0.225 to 0.245, and the decrease in absorbance in Example 3 is 0.043 to 0.058. Therefore, the difference in the degree of polarization in Examples 1 to 3 is considered to be due to the difference in the decrease in absorbance due to decolorization.
(2) The degree of polarization is higher in Example 4 than in Example 3. The stretching conditions of Example 4 are 100 ° C. and 4.5 times. The stretching conditions of Example 3 are 150 ° C. and 4.8 times. Therefore, Example 4 is more disadvantageous for the stretching conditions. On the other hand, the absorbance decrease in Example 4 is 0.583 to 0.602, and the absorbance decrease in Example 3 is 0.043 to 0.058. Therefore, Example 4 is advantageous with respect to a decrease in absorbance. Since the advantageous effect of the decrease in absorbance in Example 4 exceeded the disadvantageous effect of the stretching conditions, Example 4 is considered to have a higher degree of polarization than Example 3.
(3) Examples 5 and 6 have the same stretching conditions. However, the decrease in absorbance due to decolorization is large in Example 5 (0.243) and small in Example 6 (0.037). Therefore, it is considered that the degree of polarization differs between Example 5 and Example 6 due to the difference in absorbance decrease.
(4) The stretching temperature (110 ° C.) of Example 7 is lower than the stretching temperature (140 ° C.) of Examples 5 and 6. Therefore, Example 7 is considered to have a low degree of polarization.
(5) The reason why the degree of polarization of Comparative Examples 1, 2, and 3 is low is considered to be because the decrease in absorbance due to decolorization was not performed.

FIG. 5 illustrates a graph of absorbance (A _B ) vs. polarization degree of the dyed layer. In the examples and comparative examples in this graph, the stretching conditions are both 150 ° C. and 4.8 times. Therefore, this graph represents only the effect of decreasing absorbance due to decolorization.
This graph plots the degree of polarization when the absorbance (A _C ) of the polarizer is 0.367. Therefore, the higher the absorbance (A _B ) of the dyed layer, the more the absorbance decreases due to decolorization. Examples are Example 2, Example 1, and Example 3 in order of decreasing absorbance due to decolorization. In Comparative Example 1, decolorization is not performed. As can be seen from the graph, the degree of polarization increases as the absorbance decreases due to decolorization.

[Measuring method]
[Absorbance]
Absorbance A was calculated from equation (1) by measuring transmittance T of the sample using a spectrophotometer with integrating sphere (Dot-41 manufactured by Murakami Color Research Laboratory).
A = log ₁₀ (1 / T) (1)
Here, the transmittance T is the value of the tristimulus value Y in the XYZ color system based on the 2-degree visual field of JIS Z 8701 (1995).

[Degree of polarization]
The degree of polarization was calculated by the equation (2) by measuring the parallel transmittance H ₀ and the orthogonal transmittance H ₉₀ of the sample using a spectrophotometer with an integrating sphere (Dot-41 manufactured by Murakami Color Research Laboratory).
Polarization degree (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100 (2)
The parallel transmittance is a transmittance when two polarizers manufactured under the same conditions are stacked so that the transmission axes are parallel to each other and measured. The orthogonal transmittance is a transmittance when two polarizers manufactured under the same conditions are stacked and measured so that the transmission axes are orthogonal to each other. The parallel transmittance and the orthogonal transmittance are values of the tristimulus value Y of the XYZ color system based on the two-degree visual field of JIS Z 8701 (1995).

  The polarizer of the present invention is suitably used for liquid crystal display devices such as liquid crystal televisions, computer displays, car navigation systems, mobile phones, and game machines.

DESCRIPTION OF SYMBOLS 10 Polyvinyl alcohol-type resin layer 11 Amorphous part 12 Crystallization part 13 The arrow 14 which shows an extending | stretching direction Stretched layer 15 The arrow which shows an extending | stretching direction 16 Amorphous part 17 Crystallized part 18 Dyeing layer 19 Polyiodine ion complex 20 Polarizer 21 Delivery Part 22 Stretching roll 23 Dyeing liquid 24 Decolorizing liquid 25 Winding part 30 Support

Claims (5)

A polarizer comprising a polyvinyl alcohol-based resin layer on which iodine is adsorbed,
The polyvinyl alcohol-based resin layer has a film thickness of 0.4 to 7 μm by being stretched, has a polymer chain oriented in a certain direction, and the polymer chain includes a highly oriented crystallization part. ,
The iodine adsorbed on the polyvinyl alcohol-based resin layer is present in the polyvinyl alcohol-based resin layer in the form of a polyiodine ion complex adsorbed on the crystallization part of the polyvinyl alcohol-based resin layer, and is absorbed by the polarizer. giving dichroic, the polarizer is a absorbance from 0.359 to 0.380, a polarizer, wherein a polarization degree is as showing optical characteristics of more than 99.9%.   The polarizer according to claim 1, wherein the optical characteristics of the polarizer are such that the absorbance is 0.362 to 0.377 and the polarization degree is 99.9% or more. Characteristic polarizer. A polarizer comprising a polyvinyl alcohol-based resin layer on which iodine is adsorbed,
The polyvinyl alcohol-based resin layer has a film thickness of 0.4 to 7 μm by being stretched, has a polymer chain oriented in a certain direction, and the polymer chain includes a highly oriented crystallization part. ,
The iodine adsorbed on the polyvinyl alcohol-based resin layer is present in the polyvinyl alcohol-based resin layer in the form of a polyiodine ion complex adsorbed on the crystallization part of the polyvinyl alcohol-based resin layer, and is absorbed by the polarizer. A polarizer characterized by imparting dichroism and having an optical property with an absorbance of 0.377 or less and a polarization degree of 99.95% or more. The polarizer according to claim 3, wherein the optical characteristics of the polarizer are such that the absorbance is 0.362 to 0.377 and the polarization degree is 99.95% or more. Characteristic polarizer. 5. The polarizer according to claim 1, wherein the polyiodine ion complex is adsorbed on the crystallization part of the polymer chain in the form of I ₃ ⁻ and I ₅ ^−. A polarizer.

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